U.S. patent application number 13/273604 was filed with the patent office on 2012-04-19 for method for manufacturing piezoresistive material, piezoresistive composition and pressure sensor device.
This patent application is currently assigned to INDUSTRIAL TECHNOLOGY RESEARCH INSTITUTE. Invention is credited to Wen-Yang Chang, Yi-Lun Hsu, Li-Cheng Jheng, Kuo-Chen Shih.
Application Number | 20120090408 13/273604 |
Document ID | / |
Family ID | 45932920 |
Filed Date | 2012-04-19 |
United States Patent
Application |
20120090408 |
Kind Code |
A1 |
Jheng; Li-Cheng ; et
al. |
April 19, 2012 |
METHOD FOR MANUFACTURING PIEZORESISTIVE MATERIAL, PIEZORESISTIVE
COMPOSITION AND PRESSURE SENSOR DEVICE
Abstract
A method for manufacturing a piezoresistive material, a
piezoresistive composition and a pressure sensor device are
provided. The piezoresistive composition includes a conductive
carbon material, a solvent, a dispersive agent, an unsaturated
polyester and a crosslinking agent. The conductive carbon material
is selected from a group consisting of multi-wall nanotube,
single-wall carbon nanotube, carbon nanocapsule, graphene, graphite
nanoflake, carbon black, and a combination thereof. The solvent is
selected from a group consisting of ethyl acetate, butyl acetate,
hexane, propylene glycol mono-methyl ether acetate and a
combination thereof. The dispersive agent includes block polymer
solution with functional groups providing the affinity. The
unsaturated polyester is selected from a group consisting of an
ortho-phthalic type unsaturated polyester, an iso-phthalic type
unsaturated polyester, and a combination thereof. The crosslinking
agent is selected from a group consisting of ethyl methyl ketone
peroxide, cyclohexanone diperoxide, dibenzoyl peroxide, tert-butyl
peroxybenzoate and a combination thereof.
Inventors: |
Jheng; Li-Cheng; (Kaohsiung
City, TW) ; Chang; Wen-Yang; (Tuku Township, TW)
; Shih; Kuo-Chen; (Kaohsiung City, TW) ; Hsu;
Yi-Lun; (Tainan City, TW) |
Assignee: |
INDUSTRIAL TECHNOLOGY RESEARCH
INSTITUTE
HSINCHU
TW
|
Family ID: |
45932920 |
Appl. No.: |
13/273604 |
Filed: |
October 14, 2011 |
Current U.S.
Class: |
73/862.68 ;
252/511 |
Current CPC
Class: |
H01B 1/24 20130101; G01L
1/18 20130101 |
Class at
Publication: |
73/862.68 ;
252/511 |
International
Class: |
G01L 1/18 20060101
G01L001/18; H01B 1/24 20060101 H01B001/24 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 14, 2010 |
TW |
99135079 |
Feb 18, 2011 |
TW |
100105509 |
Oct 13, 2011 |
TW |
100137148 |
Claims
1. A method for manufacturing a piezoresistive material,
comprising: providing a piezoresistive composition comprising: a
conductive carbon material selected from a group consisting of
multi-wall carbon nanotubes, single-wall carbon nanotubes, carbon
nanocapsules, graphene, graphite nanoflakes, carbon black and a
combination thereof; a solvent selected from a group consisting of
ethyl acetate, butyl acetate, hexane, propylene glycol mono-methyl
ether acetate and a combination thereof; a dispersive agent
comprising an affinity functional groups containing block polymer
solution; an unsaturated polyester selected from a group consisting
of ortho-phthalic type unsaturated polyester, iso-phthalic type
unsaturated polyester and a combination thereof; and a crosslinking
agent selected from a group consisting of ethyl methyl ketone
peroxide, cyclohexanone diperoxide, dibenzoyl peroxide, tert-butyl
peroxybenzoate and a combination thereof, wherein the conductive
carbon material has an amount of 0.1-40 parts by weight relative to
100 parts by a total weight of the unsaturated polyester and the
conductive carbon material, the dispersive agent has an amount of
50-70 parts by weight relative to 100 parts by the weight of the
conductive carbon material, the crosslinking agent has an amount of
0.1-5 parts by weight relative to 100 parts by the weight of the
unsaturated polyester, the solvent has an amount of 10-40 parts by
weight relative to 100 parts by the weight of the unsaturated
polyester and the solvent; and curing the piezoresistive
composition for forming a piezoresistive material.
2. The method for manufacturing the piezoresistive material
according to claim 1, wherein the piezoresistive composition has a
thickness of 0.1 mm.about.5 mm.
3. The method for manufacturing the piezoresistive material
according to claim 1, wherein the piezoresistive composition
further comprises an accelerating agent, the accelerating agent has
an amount of 0.1-5 parts by weight relative to 100 parts by the
weight of the unsaturated polyester.
4. The method for manufacturing the piezoresistive material
according to claim 3, wherein the accelerating agent comprises a
cobalt based-accelerating agent.
5. The method for manufacturing the piezoresistive material
according to claim 1, a method for curing the piezoresistive
composition comprises a moisture-initiated crosslinking method, a
thermal-initiated crosslinking method, or an UV-initiated
crosslinking method.
6. The method for manufacturing the piezoresistive material
according to claim 1, a method for curing the piezoresistive
composition comprises disposing the piezoresistive composition in
an environment of 15.degree. C..about.35.degree. C. for 5 mins-24
hours and then backing the piezoresistive composition by 80.degree.
C..about.130.degree. C. for forming the piezoresistive
material.
7. A piezoresistive composition, comprising: a conductive carbon
material selected from a group consisting of multi-wall carbon
nanotubes, single-wall carbon nanotubes, carbon nanocapsules,
graphene, graphite nanoflakes, carbon black and a combination
thereof; a solvent selected from a group consisting of ethyl
acetate, butyl acetate, hexane, propylene glycol mono-methyl ether
acetate and a combination thereof; a dispersive agent comprising an
affinity functional groups containing block polymer solution; an
unsaturated polyester selected from a group consisting of
ortho-phthalic type unsaturated polyester, iso-phthalic type
unsaturated polyester and a combination thereof; and a crosslinking
agent selected from a group consisting of ethyl methyl ketone
peroxide, cyclohexanone diperoxide, dibenzoyl peroxide, tert-butyl
peroxybenzoate and a combination thereof, wherein the conductive
carbon material has an amount of 0.1-40 parts by weight relative to
100 parts by a total weight of the unsaturated polyester and the
conductive carbon material, the dispersive agent has an amount of
50-70 parts by weight relative to 100 parts by the weight of the
conductive carbon material, the crosslinking agent has an amount of
0.1-5 parts by weight relative to 100 parts by the weight of the
unsaturated polyester, the solvent has an amount of 10-40 parts by
weight relative to 100 parts by the weight of the unsaturated
polyester and the solvent.
8. The piezoresistive composition according to claim 7, further
comprising an accelerating agent.
9. The piezoresistive composition according to claim 8, wherein the
accelerating agent has an amount of 0.1-5 parts by weight relative
to 100 parts by the weight of the unsaturated polyester.
10. A pressure sensor device, comprising: a first plate having a
first conductive structure on a surface of which; a second plate
having a second conductive structure on a surface of which; and a
piezoresistive material electrically connected between the first
conductive structure and the second conductive structure, wherein
the piezoresistive material is manufactured by the method according
to one of claims 1-6.
Description
[0001] This application claims the benefits of Taiwan application
Serial No. 99135079, filed Oct. 14, 2010, Taiwan application Serial
No. 100105509, filed Feb. 18, 2011, and Taiwan application Serial
No. 100137148, filed Oct. 13, 2011, the disclosure of which is
incorporated by reference herein in its entirety.
BACKGROUND
[0002] 1. Technical Field
[0003] The disclosure relates in general to a method for
manufacturing a piezoresistive material, a piezoresistive
composition and a pressure sensor device and more particularly to a
piezoresistive material manufactured by using an unsaturated
polyester.
[0004] 2. Description of the Related Art
[0005] A piezoresistive material can be applied for an electronic
component for a sensor such as a pressure sensor, a tactile sensor,
a flow sensor, etc. For manufacturing the piezoresistive material,
a conductive silicon rubber composite is used. The conductive
silicon rubber composite is mainly formed by dispersing micro-scale
conductive materials in a silicon rubber based material.
[0006] However, the repeatability of the piezoresistive
characteristic of the conductive silicon rubber composite is not
good. It needs performing cyclic compression for many times for a
stable piezoresistive characteristic curve. The successive, cyclic
compression treatment increases manufacturing cost and time. In
addition, the required response time for the resistance of the
conductive silicon rubber composite to reach its steady state is
long (>10 sec). It results in a response time delay of the
pressure sensor device.
SUMMARY
[0007] According to one aspect of the present disclosure, a method
for manufacturing a piezoresistive material is provided. The method
comprises following steps. A piezoresistive composition is
provided. The piezoresistive composition comprises a conductive
carbon material, a solvent, a dispersive agent, an unsaturated
polyester, and a crosslinking agent. The conductive carbon material
is selected from a group consisting of multi-wall carbon nanotubes,
single-wall carbon nanotubes, carbon nanocapsules, graphene,
graphite nanoflakes, carbon black and a combination thereof. The
solvent is selected from a group consisting of ethyl acetate, butyl
acetate, hexane, propylene glycol mono-methyl ether acetate and a
combination thereof. The dispersive agent comprises an affinity
functional groups containing block polymer solution. The
crosslinking agent is selected from a group consisting of ethyl
methyl ketone peroxide, cyclohexanone diperoxide, dibenzoyl
peroxide, tert-butyl peroxybenzoate and a combination thereof. The
unsaturated polyester is selected from a group consisting of
ortho-phthalic type unsaturated polyester, iso-phthalic type
unsaturated polyester and a combination thereof. The conductive
carbon material has an amount of 0.1-40 parts by weight relative to
100 parts by a total weight of the unsaturated polyester and the
conductive carbon material. The dispersive agent has an amount of
50-70 parts by weight relative to 100 parts by the weight of the
conductive carbon material. The crosslinking agent has an amount of
0.1-5 parts by weight relative to 100 parts by the weight of the
unsaturated polyester. The solvent has an amount of 10-40 parts by
weight relative to 100 parts by the weight of the unsaturated
polyester and the solvent. The piezoresistive composition is cured
for forming a piezoresistive material.
[0008] According to another aspect of the present disclosure, a
piezoresistive composition is provided. The piezoresistive
composition comprises a conductive carbon material, a solvent, a
dispersive agent, an unsaturated polyester, and a crosslinking
agent. The conductive carbon material is selected from a group
consisting of multi-wall carbon nanotubes, single-wall carbon
nanotubes, carbon nanocapsules, graphene, graphite nanoflakes,
carbon black and a combination thereof. The solvent is selected
from a group consisting of ethyl acetate, butyl acetate, hexane,
propylene glycol mono-methyl ether acetate and a combination
thereof. The dispersive agent comprises an affinity functional
groups containing block polymer solution. In the present
disclosure, the unsaturated polyester may be selected from a group
consisting of ortho-phthalic type unsaturated polyester,
iso-phthalic type unsaturated polyester and a combination thereof.
The crosslinking agent is selected from a group consisting of ethyl
methyl ketone peroxide, cyclohexanone diperoxide, dibenzoyl
peroxide, tert-butyl peroxybenzoate and a combination thereof. The
conductive carbon material has an amount of 0.1-40 parts by weight
relative to 100 parts by a total weight of the unsaturated
polyester and the conductive carbon material. The dispersive agent
has an amount of 50-70 parts by weight relative to 100 parts by the
weight of the conductive carbon material. The crosslinking agent
has an amount of 0.1-5 parts by weight relative to 100 parts by the
weight of the unsaturated polyester. The solvent has an amount of
10-40 parts by weight relative to 100 parts by the weight of the
unsaturated polyester and the solvent.
[0009] According to yet another aspect of the present disclosure, a
pressure sensor device is provided. The pressure sensor device
comprises a first plate, a second plate and a piezoresistive
material. The first plate has a first conductive structure on a
surface of which. The second plate has a second conductive
structure on a surface of which. The piezoresistive material is
electrically connected between the first conductive structure and
the second conductive structure. The piezoresistive material is
manufactured by the above method.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 illustrates a top view of a first plate of a pressure
sensor device.
[0011] FIG. 2 illustrates a top view of a second plate of a
pressure sensor device.
[0012] FIG. 3 illustrates a cross-section view of a pressure sensor
device.
[0013] FIG. 4 shows a time-resistance relation of a pressure sensor
device measured by the test equipment.
[0014] FIG. 5 shows a time-resistance relation of the pressure
sensor device using the piezoresistive material of Example as a
main body measured by the test equipment.
[0015] FIG. 6 illustrates resistance change of the pressure sensor
device using the piezoresistive material as a function of applied
force of Example as a main body measured by the test equipment.
[0016] FIG. 7 illustrates a time-resistance relation of the
pressure sensor device using the silicon rubber piezoresistive
material (Comparative example) as a main body measured by the test
equipment.
DETAILED DESCRIPTION
[0017] Embodiments of the present disclosure disclose a
piezoresistive material. A method for manufacturing the
piezoresistive material comprises following steps. A piezoresistive
composition is provided. In addition, the piezoresistive
composition is cured for forming the piezoresistive material. For
example, the piezoresistive composition may be coated onto a
substrate and then cured.
[0018] The piezoresistive composition comprises a conductive carbon
material, a solvent, a dispersive agent, an unsaturated polyester,
and a crosslinking agent. The conductive carbon material is
uniformly dispersed in the piezoresistive composition. Therefore,
the piezoresistive material has good properties such as resistance
constancy and piezoresistive repeatability.
[0019] The unsaturated polyester may be selected from a group
consisting of ortho-phthalic type unsaturated polyester,
iso-phthalic type unsaturated polyester and a combination
thereof.
[0020] The conductive carbon material may be selected from a group
consisting of multi-wall carbon nanotubes, single-wall carbon
nanotubes, carbon nanocapsules, graphene, graphite nanoflakes,
carbon black and a combination thereof. The conductive carbon
material has an amount of 0.1-40 parts by weight relative to 100
parts by a total weight of the unsaturated polyester and the
conductive carbon material. In an exemplary embodiment, the
conductive carbon material is the multi-wall carbon nanotube or
single-wall carbon nanotube having a high aspect ratio (for
example, about 1000:1) and thus having a good conductive property
and a strong mechanical strength (or tenacity). Therefore, the
piezoresistive material with a good conductive property and
mechanical strength (or tenacity) can be formed by using a small
amount of the multi-wall carbon nanotubes or single-wall carbon
nanotubes.
[0021] The solvent may be selected from a group consisting of ethyl
acetate, butyl acetate, hexane, propylene glycol mono-methyl ether
acetate and a combination thereof. The solvent has an amount of
10-40 parts, exemplarily 30 parts, by weight relative to 100 parts
by the weight of the unsaturated polyester and the solvent. The
dispersive agent comprises an affinity functional groups containing
block polymer solution. The dispersive agent may comprise, for
example, BYK 164 (BYK corporation) or BYKUMEN (BYK corporation).
The dispersive agent has an amount of 50-70 parts by weight
relative to 100 parts by the weight of the conductive carbon
material.
[0022] For example, the unsaturated polyester is a material
obtained by cross-linking and curing a liquid polyester oligomer or
polyester polymer having unsaturated double bond. The structure of
the unsaturated polyester may comprise an aromatic structure. The
unsaturated polyester does not have thermoplastic property.
[0023] The crosslinking agent may be selected from a group
consisting of ethyl methyl ketone peroxide, cyclohexanone
diperoxide, dibenzoyl peroxide, tert-butyl peroxybenzoate and a
combination thereof. The crosslinking agent has an amount of 0.1-5
parts or 0.5-1.5 parts, exemplarily 0.8 parts, by weight relative
to 100 parts by the weight of the unsaturated polyester. In some
embodiments, the piezoresistive composition may also comprise an
accelerating agent that helps the crosslinking agent's function.
The accelerating agent may comprise a cobalt based-accelerating
agent, such as cobalt naphthenate. The accelerating agent has an
amount of 0.1-5 parts or 0.3-1 parts, exemplarily 0.5 parts, by
weight relative to 100 parts by the weight of the unsaturated
polyester.
[0024] A method for uniformly dispersing the conductive carbon
material in the piezoresistive composition may comprise, for
example, a sonication, a wet grinding, a vigorously mechanical
stirring, etc.
[0025] In embodiments, the piezoresistive composition is a fluid,
and thus can be coated on a substrate by a printing method
comprising, for example, a screen printing method or a stencil
printing method. The coating method may be adjusted according to a
viscosity of the piezoresistive composition. The method of
embodiments of the present disclosure may be applied to a
roll-to-roll continuous process. The cost is low and the
manufacturing speed is high.
[0026] The method of embodiments of the present disclosure may be
applied to a substrate that has a big area. In addition, the
substrate may be flexible such as polyethylene terephthalate (PET),
polyethylene naphthalate (PEN), or polyamide (PI). The substrate
may also be glass.
[0027] A method for curing the piezoresistive composition may
comprise, for example, a moisture-initiated crosslinking method, a
thermal-initiated crosslinking method, or an UV-initiated
crosslinking method. The method may be adjusted according to the
unsaturated polyester or the crosslinking agent of the
piezoresistive composition.
[0028] In embodiments, for example, the piezoresistive composition
having a thickness of 0.1 mm.about.5 mm is disposed in an
environment of 15.degree. C..about.35.degree. C. for at least 5
minutes, for example 5 minutes-24 hours, or for example 30 minutes
for cross-linking the piezoresistive composition. Then the
piezoresistive composition is backed by 80.degree.
C..about.130.degree. C. for removing the solvent so as to form the
piezoresistive material. The piezoresistive composition can be
cross-linked in an ambient temperature without using an additional
heating or cooling system. Thus the manufacture cost is low.
[0029] The piezoresistive material belongs to a high surface energy
material, and thus has a strong adhesive strength with, for
example, the flexible substrate. The piezoresistive material may be
applied for a flow sensor, a deformation sensor, etc.
[0030] In embodiments, the piezoresistive material is applied for a
pressure sensor device. FIG. 1 illustrates a top view of a first
plate 2 of the pressure sensor device. FIG. 2 illustrates a top
view of a second plate 4 of the pressure sensor device. FIG. 3
illustrates a cross-section view of the pressure sensor device
drawn along AB line of FIG. 1 and FIG. 2.
[0031] As shown in figures, the pressure sensor device comprises
the first plate 2, the second plate 4 and the piezoresistive
material 6. The first plate 2 has a first conductive structure 8 on
a surface of which. The first conductive structure 8 may have a
first electrode pad 10 and a first trace 12 electrically connected
to each other.
[0032] The second plate 4 has a second conductive structure 14 on a
surface of which. The second conductive structure 14 has a second
electrode pad 16 and a second trace 18 electrically connected to
each other.
[0033] In embodiments, the piezoresistive material 6 is
electrically connected between the first electrode pad 10 of the
first conductive structure 8 and the electrode pad 16 of the second
conductive structure 14. In detail, for example, the piezoresistive
material 6, the first electrode pad 10 and the electrode pad 16
overlap.
[0034] In one embodiment, the first trace 12 and the second trace
18 are arranged to be perpendicular to each other. However, the
present disclosure is not limited to this. In other embodiments,
for example, the first trace 12 and the second trace 18 are
arranged to be parallel to each other. In some embodiments, the
trace is designed to have other kinds of multi-layer structure such
as a three-layer structure.
[0035] The advantages of the present disclosure are illustrated
with the following examples of the present disclosure and
comparative examples.
Preparing Piezoresistive Material
EXAMPLE
Unsaturated Polyester Based Piezoresistive Material
[0036] A mixture comprising 0.609 g multi-wall carbon nanotubes,
21.866 g butyl acetate solvent, and 0.365 g BYK/164 (BYK
corporation) dispersive agent are well mixed for 1 hour by a
vigorously mechanical stirring for uniformly dispersing the
multi-wall carbon tubes for forming a carbon material containing
suspension solution. The multi-wall carbon tubes are uniformly
dispersed in the carbon material containing suspension solution. 40
g liquid ortho-phthalic type unsaturated polyester
(Changhung/ETERSET 2740P) and the carbon material containing
suspension solution are uniformly mixed at a stirring speed of 600
rpm for 6 hours by a high-torque mechanical stirrer for forming a
mixture solution. Before coating, a coating composition is formed
by uniformly stirring 0.325 g ethyl methyl ketone peroxide (MEKPO)
(crosslinking agent), 0.203 g cobalt naphthenate accelerating
agent, and the mixture solution.
[0037] Next, the coating composition having a thickness of about
0.5 mm is coated on a flexible PET by a stencil printing method.
Next, the coating composition is cured by crosslinking at the room
temperature of 15.degree. C..about.35.degree. C. for 30 minutes.
Next, the crosslinked coating composition is baked at 80 for
removing the butyl acetate solvent for forming a piezoresistive
material.
COMPARATIVE EXAMPLE
Silicon Rubber Based Piezoresistive Material
[0038] A mixture comprising 1.316 g multi-wall carbon nanotubes,
2.78 g butyl acetate solvent, 0.790 g BYK/164 (BYK corporation)
dispersive agent, and 25 g two-component type thermal-initiated
crosslinking liquid silicon rubber A (Dow Corning/SOR6500A) are
uniformly mixed at a stirring speed of 600 rpm for 6 hours by a
high-torque mechanical stirrer for forming a mixture solution A. In
the meantime, a mixture comprising 1.316 g multi-wall carbon
nanotubes, 2.78 g butyl acetate solvent, 0.790 g BYK/164 dispersive
agent, and 25 g two-component type thermal-initiated crosslinking
liquid silicon rubber B (Dow Corning/SOR6500B) are uniformly mixed
at a stirring speed of 600 rpm for 6 hours by a high-torque
mechanical stirrer for forming a mixture solution B. Before
coating, a coating composition is formed by uniformly stirring the
mixture solution A and the mixture solution B with a ratio of
1:1.
[0039] Next, the coating composition having a thickness of 0.5 mm
is coated on a flexible PET by a stencil printing method. Next, the
coating composition is cured by crosslinking and the butyl acetate
solvent of which is removed at 120 for 10 minutes for forming a
piezoresistive material.
Pressure Sensor Device
[0040] In the embodiment, the pressure sensor device as shown in
FIG. 1 to FIG. 3 is used. The first plate 2 and the second plate 4
are both constructed from a polyimide (PI) copper foil laminate.
The first conductive structure 8 and the second conductive
structure 14 are formed by patterning the copper foil by an etching
process. The piezoresistive material 6 is formed by coating the
piezoresistive composition onto the first electrode pad 10 of the
first conductive structure 8 by a stencil printing method, and then
curing the piezoresistive composition.
[0041] Equipment for testing the pressure sensor device is
constructed with a force measurement gauges, a LCR meter, and a
six-axis micro platform. A test is performed by contacting a single
pixel with a cylindrical rod. The bottom end of the cylindrical rod
is flat. The force measurement gauges used a continuous
force-sensing mode. A resistance of the pressure sensor device is
measured by the LCR meter using a frequency of 1 kHz.
[0042] FIG. 4 and FIG. 5 respectively show time-resistance
relations of the pressure sensor device using the unsaturated
polyester based piezoresistive material (Example) as a main body
measured by applying 10N and 15N for three times repeatedly by the
test equipment. From the results of FIG. 4 and FIG. 5, it is found
that the response time of the pressure sensor device, defined as
the required time to reach the steady state, is extremely short,
and the resistance exhibits an equilibrium state. The resistance
does not change much under the same force applied at different
times. It indicates the pressure sensor device has fast response
speed and good resistance constancy. Thus, the pressure sensor
device is suitable for applications.
[0043] FIG. 6 illustrates a force-resistance relation of the
pressure sensor device using the unsaturated polyester based
piezoresistive material (Example) as a main body measured by
applying different forces repeatedly by the test equipment. From
the result of FIG. 6, it is found that the pressure sensor device
has a good characteristic curve of force to resistance and
repeatability.
[0044] FIG. 7 illustrates a time-resistance relation of the
pressure sensor device using the silicon rubber based
piezoresistive material (Comparative example) as a main body
measured by applying 5N and 10N by the test equipment. From the
result of FIG. 7, it is found that the resistance of the pressure
sensor device needs a long time for reaching the steady state. The
resistance is relatively not stable, especially when a low force is
applied.
[0045] The piezoresistive material has the conductive carbon
material uniformly dispersed therein, and thus has a good
resistance constancy and piezoresistive repeatability. As the
conductive carbon material is the carbon nanotubes, the
piezoresistive material, using even a small amount of carbon
nanotubes, can have a good conductive property and mechanical
strength (tenacity). The piezoresistive composition using the
unsaturated polyester has a liquid phase at room temperature, and
thus the conductive carbon material can be uniformly mixed therein
at room temperature. In addition, the unsaturated polyester is a
cheap material. Therefore, the manufacturing cost for the
piezoresistive material can be reduced.
[0046] The piezoresistive composition is a fluid, and thus can be
coated on the substrate by a printing method and applied in a
roll-to-roll continuous process. The cost is low and the
manufacturing speed is high. In addition, the piezoresistive
composition can be applied for a big area process. Moreover, the
piezoresistive material is a high surface energy material, and thus
has a strong adhesive strength with the flexible substrate having a
high surface energy, such as PET, PEN or PI, or a glass.
[0047] While the disclosure has been described by way of example
and in terms of the exemplary embodiment(s), it is to be understood
that the disclosure is not limited thereto. On the contrary, it is
intended to cover various modifications and similar arrangements
and procedures, and the scope of the appended claims therefore
should be accorded the broadest interpretation so as to encompass
all such modifications and similar arrangements and procedures.
* * * * *